1. Field of the Invention
The present invention generally relates to an infrared gas analyzer.
2. Description of the Prior Art
FIG. 18 shows a conventional infrared gas analyzer. Referring to FIG. 18, reference numerals 71, 72 designate a measuring cell and a reference cell arranged in parallel to each other. Although not shown in detail, both end portions of the respective cells 71, 72 are sealed with a cell window formed of infrared radiation transparent materials. Measuring cell 71 is supplied with a sample gas, as shown by the arrows, while the reference cell 72 is filled with a reference gas. Reference numeral 73 designates a radiation source at one end of cells 71, 72 used to transmit infrared radiation through cells 71, 72.
Reference numerals 74, 75 designate a detector comprising, for example, a pyrosensor placed at the end of cells 71, 72, respectively, for receiving infrared radiation passing through the cells 71, 72. Said detector 74 corresponding to measuring cell 71 is provided with a band pass filter 74a transmitting infrared radiation of a characteristic absorption band of a component gas to be measured (for example CO.sub.2) therethrough while detector 75, corresponding to the reference cell 72, is provided with a band pass filter 75a transmitting infrared radiation having wavelengths out of said absorption band for said component gas to be measured. Reference numeral 76 designates a chopper arranged between cells 71, 72 and detectors 74, 75 and driven by a motor (not shown).
In the infrared gas analyzer described above, when measuring cell 71 is supplied with a sample gas and radiation source 73 is switched on to transmit infrared radiation through cells 71, 72 and chopper 76 is rotated, detecting signals are put out from detectors 74, 75 allowing a concentration of the component gas to be measured by analyzing the signals in an operating portion (not shown).
However, in the above-described conventional infrared gas analyzer, radiation source 73 is constantly on prior to measurement so that a temperature suitable for the measurement of the component gas may be arrived at while chopper 76 is continuously rotated. Thus, it takes considerable time and electric power for preparation prior to measurement and stabilization. In short, a conventional infrared gas analyzer can be said to be an energy consumption type. In addition, a disadvantage occurs in that heat generated when the radiation source 73 is active, and the motor is being rotated, as described above, is transmitted to detectors 74, 75, whereby said outputs of the detectors 74, 75 are influenced by a temperature-drift. Furthermore, chopper 76 is provided in addition to radiation source 73, cells 71, 72 and detectors 74, 75, so that a conventional infrared gas analyzer is undesirably large as a whole.